Resistors made of resistor material supported on a substrate and having electrodes at two ends of the material are trimmed by lasers to precisely remove material between the electrodes so as to achieve the desired resistance for the resistor. By removing material, the flow of electricity is impeded, thereby increasing resistance.
Fixed resistance resistors typically have rectangular patches of resistor material on the substrate, and trimming of these rectangular resistors has typically involed a plunge cut (a single slice extending from one side into the material transverse to the direction between electrodes), an L-cut (two legs, one extending in from a side transverse to the direction between electrodes and one parallel to the direction), a U-cut (three legs, two extending from a side and transverse to the direction and one parallel to it), or a scan cut (repetitive overlapping cuts that remove a large portion of material).
Potentiometers have been made using curved patches of resistor material having inner and outer boundaries that are concentric arcs; the material is connected in the circuit by a fixed electrode at one end and a rotatable contact that can be moved to contact the resistor material at various positions along its curved length. Such curved resistors are typically trimmed by making a plurality of plunge cuts extending radially from the inner curved boundary and spaced from each other along the curved patch of resistor material.